Low profile catheter for increasing lumen size of a blood vessel and guide wire therefor

ABSTRACT

A low profile catheter for increasing lumen size of a blood vessel includes a catheter shaft which carries an inflatable balloon at its distal end. A guide wire is positioned in the catheter shaft to extend beyond the balloon, and the guide wire defines a keyed portion having a cross-sectional shape which is other than round. A keyed coupling number is carried by the catheter shaft and coupled to the keyed portion of the guide wire to transmit torque from the catheter shaft to the guide wire while permitting relative axial movement between the catheter shaft and the guide wire. Alternately, wound coil springs are mounted to the catheter shaft by a spyder. The coil springs seize the guide wire in response to rotation, but allow longitudinal movement of the guide wire in the absence of rotation.

BACKGROUND OF THE INVENTION

This invention relates to a low profile catheters such as ballooncatheters used to increase the lumen size of a blood vessel, and toguide wires used with such catheters.

Catheters such as balloon catheters have been used for some time toincrease the lumen size of vessels such as coronary blood vessels.Typically, a flexible guide wire is inserted into a selected vessel, andthe guide wire then guides the balloon catheter to the treatment site.Packard U.S. Pat. No. 4,646,742 describes one prior art balloon catheterused in an angioplasty procedure. A coil spring guide wire passesthrough the catheter, beyond the distal end of the catheter and theballoon. Fogarty U.S. Pat. No. 4,606,347 and Samson U.S. Pat. No.4,641,654 (FIG. 1b) show other balloon catheters which utilize suchguide wires. In the catheter shown in the Fogarty patent a seal isprovided near the distal end of the catheter between the catheter andthe guide wire.

This prior art approach requires that the guide wire itself besufficiently rotationally rigid to transmit rotation from its proximalto distal ends when it is rotated to steer the distal end of the guidewire into a desired vessel. As catheters and guide wires are designedfor use with increasingly smaller diameter blood vessels, it may bedifficult to ensure that the wire has an adequately small diameter yetis adequately torsionally rigid.

Another approach of the prior art is illustrated in the systemsdescribed in Mar U.S. Pat. No. 4,771,778, Mar U.S. Pat. No. 4,793,350,Samson U.S. Pat. No. 4,582,181, and Samson U.S. Pat. No. 4,641,654 (FIG.1a). In these catheters the guide wire is secured to the distal end ofthe catheter, distally of the balloon, such that a fixed length of theguide wire extends beyond the distal end of the catheter. With thisapproach, the guide wire is formed as a permanent part of the catheter,and it is therefore not possible to remove the catheter from the bloodvessel without simultaneously removing the guide wire. In certainmedical procedures it is preferred to leave the guide wire in place atthe treatment site while a first catheter is removed from the guidewire. Then a second catheter, possibly different in shape or functionfrom the first, can be guided by the guide wire back to the originaltreatment site quickly and reliably. Of course, such procedures cannotbe performed with a catheter in which the guide wire is permanentlyaffixed to the catheter.

Horzewski U.S. Pat. No. 4,932,959 discloses a vascular dilation catheterwhich receives a removable guide wire. The catheter shaft defines anannular portion which may be inflated to releasably secure the catheterto the guide wire to allow the two to be advanced as a single unit. Thetorque transmitting characteristics of the annular inflatable portionare not discussed. However, it is clear that the inflatable portion mustbe inflated from the distal end of the catheter to secure the catheterto the guide wire and then deflated from the distal end of the catheterto release the catheter from the guide wire. The time required toinflate and deflate the annular portion may limit the speed with whichthe guide wire can be shifted between the secured and released modes ofuse.

Accordingly, it is an object of this invention to provide an improvedlow profile catheter for increasing the lumen size of a blood vessel,which utilizes the catheter shaft to transmit torque to the guide wireat a point near the distal end of the guide wire.

It is another object of this invention to provide such a catheter inwhich torque is transmitted from the catheter shaft to the guide wirewhile permitting relative axial movement therebetween.

It is another object of this invention to provide such a catheter inwhich torque is automatically transmitted from the catheter to the guidewire when the catheter is rotated with respect to the guide wire, andwherein the guide wire is automatically permitted to move longitudinallywhen the guide wire is advanced with respect to the catheter.

It is yet another object of this invention to provide such a catheter inwhich the guide wire is shaped to allow the catheter to be removed fromthe guide wire, in order to allow the guide wire to be left in place atthe treatment site while the first catheter is removed and replaced witha second.

SUMMARY OF THE INVENTION

According to this invention a low profile catheter is provided forincreasing lumen size of a blood vessel. This catheter includes acatheter shaft having proximal and distal ends and defining an axisextending therebetween. Means are carried by the distal end of the shaftfor increasing lumen size of a blood vessel in which the catheter shaftis positioned. A guide wire is positioned in the catheter shaft so as toextend beyond the distal end of the catheter shaft and the lumen sizeincreasing means. Means are provided for automatically transmittingtorque from the catheter shaft to the guide wire when the catheter shaftis rotated with respect to the guide wire and for automaticallypermitting relative axial movement therebetween when the guide wire isadvanced with respect to the catheter shaft.

In the preferred embodiments described below the lumen size increasingmeans comprises an inflatable balloon. Of course, those skilled in theart will recognize that other types of lumen size increasing means canbe used, such as atherectomy devices that rely on ablation techniques(light, ultrasonic or hydraulic) or cutting elements of various types.

In the first preferred embodiment described below the torquetransmitting means comprises a sleeve carried by the catheter shaft thatdefines an other than round opening, and a keyed portion of the guidewire shaped to fit into the other than round opening in such a way thatthe guide wire is slidable in the sleeve, yet the guide wire receivestorque via the sleeve from the catheter shaft itself. Because thecatheter shaft is of relatively larger diameter than the guide wire, thecatheter shaft is well suited to transmit torque from its proximal endto the torque transmitting means.

In the second preferred embodiment described below the torquetransmitting means comprises a pair of coil springs configured to seizethe guide wire when the catheter shaft is rotated and to allow axialmovement of the guide wire in the absence of rotation of the cathetershaft.

This invention is also directed to the low profile dilation catheter andto the keyed guide wire as separate elements.

The invention itself, together with further objects and attendantadvantages, will best be understood by reference to the followingdetailed description, taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view in partial cutaway of a lowprofile catheter assembly which incorporates a first presently preferredembodiment of this invention.

FIG. 2 is a cross-sectional view taken along line 2--2 of FIG. 1.

FIG. 3 is a fragmentary side view in partial cutaway of the guide wireincluded in the catheter assembly of FIG. 1.

FIG. 4 is a cross-sectional view taken along line 4--4 of FIG. 3.

FIG. 5 is a longitudinal sectional view of portions of a low profilecatheter assembly which incorporates a second preferred embodiment ofthis invention.

FIG. 6 is a cross sectional view taken along line 6--6 of FIG. 5.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Turning now to the drawings, FIG. 1 shows a longitudinal sectional viewof a low profile catheter assembly 10. The catheter assembly 10 includesa catheter having a catheter shaft 12 which defines a proximal end 14and a distal end 16. In this embodiment, the catheter shaft 12 istorsionally rigid and is formed of a ferrous metal alloy.

The distal end 16 of the shaft 12 carries a means for increasing thelumen size of a blood vessel in which the shaft 12 is placed. In thisembodiment, the lumen size increasing means includes an inflatableballoon 20 which is sealed at its proximal end to an outer tube 22 andat its distal end to an inner tube 24. The outer tube 24 is in turnsealed to the distal end of the shaft 12. The inner tube 24 extendsaxially through the balloon 20 and is sealed at its proximal end to anecked down portion of the shaft 12. As pointed out above, thisinvention is not limited to use with balloon type lumen size increasingmeans. Rather, it can also be adapted for use with other means forperforming this function, such as devices including lasers or cutting,scraping or abrading edges.

Simply by way of example, in this preferred embodiment the inner tube 24is formed of high density polyethylene and has an outer diameter of0.016 inch and a wall thickness of 0.0025 inch. The balloon 20 can beformed of any conventional material such as a polyolefin copolymer in athickness of 0.001-0.003 inches, depending on balloon diameter, and theouter tube 22 can be formed of a material such as high densitypolyethylene having an outer diameter of 0.026 inch and a wall thicknessof 0.003 inch. The shaft 12 can be formed from 304 stainless steel withan outer diameter of 0.026 inch and a wall thickness of 0.0035 inch.

FIGS. 1 and 3 show two views of a guide wire 30 that is mounted insidethe shaft 12 as part of the catheter assembly 10. The guide wire 30defines a proximal end 32 and a distal end 34. The distal end 34 forms aflexible end portion 36 that is configured to follow a blood vesselwithout damaging the walls of the vessel.

Intermediate the proximal and distal ends, the guide wire 30 defines akeyed portion 38 which defines a pair of opposed flats 40 as shown inFIG. 2. The keyed portion 38 is positioned in FIG. 1 near the distal end16 of the shaft 12. The guide wire 30 defines a region 42 extendingproximally of the keyed portion 38 to the proximal end 32. This region42 is sized no larger than the keyed portion 38, and in this embodimentis of reduced diameter as compared with the keyed portion 38. The guidewire 30 defines an enlarged region 44 which is positioned immediatelydistally of the keyed portion 38. The transition between the enlargedregion 44 and the keyed portion 38 is formed by transverse shoulder 48.The maximum diameter of the guide wire 30 is defined at the flexible endportion 36. This flexible end portion 36 includes a coil spring 50 whichis brazed at each end to the guide wire 30 as indicated at referencenumeral 52. The distal end 34 of the guide wire 30 defines an enlargedend 54 sized to fit within the coil spring 50. Proximally of theenlarged end 54 is a neck region 56, shaped as shown in FIG. 4.

In this preferred embodiment the guide wire 30 is formed of a solid mainwire which can be formed of a ferrous alloy such as 304 stainless steel.The coil spring 50 can for example be formed of a radiopaque wire havinga diameter of 0.002 inches. Simply to define the presently preferredembodiment of this invention, the following table lists preferreddimensions for the diameters D1-D5 and the lengths L1-L5, as shown inFIG. 3:

    ______________________________________                                        MEASUREMENT  PREFERRED DIMENSION (inches)                                     ______________________________________                                        D1           0.008                                                            D2           0.0095                                                           D3           0.0078                                                           D4           0.0055                                                           D5           0.100                                                            L1           4.00                                                             L2           7.00                                                             L3           11.00                                                            L4           11.93                                                            L5           69. (175 cm)                                                     ______________________________________                                    

The flats 40 in this embodiment have an axial length of 15 cm, thoughflats 40 may also be used which are less than 10 cm in length.

The catheter 10 includes means for transmitting torque from the shaft 12to the guide wire 30 and allowing axial movement therebetween. In thispreferred embodiment, the torque transmitting means is implemented as akeyed sleeve 64 which is secured to the distal end of the shaft 12 by atransversely oriented plate 60. In the embodiment shown in FIG. 1 theplate 60 and the sleeve 64 are integrally formed with the shaft 12. Ofcourse, this detail of construction is not to be considered as anessential feature of this invention, and multiple pieces can be securedtogether to achieve the same function.

As shown in FIG. 2, the plate 60 defines two openings 62 which areprovided to pass an inflating fluid between the interior of the shaft 12and the balloon 20. The sleeve 64 defines an interior opening 66 whichis other than round in cross section. The opening 66 defines a pair offlats 68 which are shaped to engage the flats 40 so as to preventrelative rotation between the shaft 12 and the guide wire 30. The fitbetween the keyed portion 38 of the guide wire 30 and the opening 66 ofthe sleeve 64 is a sliding fit that allows the guide wire 30 to be movedaxially with respect to the catheter shaft 12. Nevertheless, because ofthe mating engagement of the flats 68, 40 rotational forces applied tothe proximal end 14 of the shaft 12 are applied via the sleeve 64 andthe keyed portion 38 to the guide wire 30 at a point near the distal end34 of the guide wire 30. The shoulder 48 is shaped to engage the distalend of the sleeve 64 to provide a positive stop. Thus, by moving theguide wire 30 until the shoulder 48 contacts the sleeve 64, it can beensured that the sleeve 64 is in torque transmitting engagement with thekeyed portion 38 of the guide wire 30.

An inflation manifold 80 is secured to the proximal end 14 of the shaft12 to accommodate introduction of an inflating fluid into the interiorof the shaft 12. This inflation manifold 80 can be connected in aconventional manner to a source of pressurized inflating fluid (notshown) when the balloon 20 is to be inflated. The inflation manifold 80also functions as a means for applying torque to the proximal end 14 ofthe shaft 12. In use, the inflation manifold 80 can be rotated to rotatethe shaft 12 and thereby apply rotating torques to the keyed portion 38of the guide wire 30. A seal 82 is provided on the inflation manifold 80to prevent the release of inflating fluid around the guide wire 30. Thisseal 82 accommodates relative axial movement between the guide wire 30and the shaft 12.

In use, the distal end 34 of the guide wire 30 is provided with aprebent curvature (not shown), and the guide wire 30 is assembled withthe shaft 12 as shown in FIG. 1. This assembly is then inserted in theconventional manner into the vascular system of a patient. The guidewire 30 is used to guide the balloon 20 into the desired arterialbranch. This is done by advancing the distal end 34 of the guide wire 30into the desired arterial branch. When rotation is required to orientthe prebent distal end 34, the shaft 12 is positioned to engage thesleeve 64 with the keyed portion 38, and then the inflation manifold 80is manually rotated. The shaft 12 is torsionally rigid as explainedabove, and rotational movement applied to the proximal end 14 istransmitted substantially completely to the distal end 16, where it isapplied to the keyed portion 38 of the guide wire 30. The portion of theguide wire 30 between the keyed portion 38 and the distal end 34 hassufficient torsional rigidity to rotate the distal end 34 of the guidewire 30 smoothly and reliably. In this embodiment the coil spring 50 isformed of a radiopaque alloy including a metal such as platinum to allowthe position of the coil spring 50 to be visualized on a flouriscopeduring the steering operation.

In this way, the shaft 12 and guide wire 30 cooperate to provide aneasily steerable guide wire 30 which is nevertheless extremely small indiameter. Because the shaft 12 itself transmits torque to the keyedportion 38, the torsional rigidity of the guide wire proximal to thekeyed portion 38 may be low with-out interfering with the ease withwhich the distal end 34 may be rotated and steered. Thus, this inventionhas particular advantages in extremely small diameter catheters which bynecessity require even smaller diameter guide wires (less than 0.020inches in diameter), which may not be well suited to transmit torqueseffectively over a length of more than 150 cm. In the preferredembodiment described above the keyed region 38 is positionedapproximately 12 inches proximally of the distal end 34. The overalllength of the guide wire 30 is 175 cm or about 69 inches. Thus, thekeyed portion 38 is spaced from the distal end 34 by no more than about20 percent of the overall length of the guide wire 30.

The catheter 10 provides the important advantage that once the guidewire 30 has been used to advance the balloon 20 to a desired treatmentsite, the shaft 12 and the balloon 20 can be removed from the proximalend 32 of the guide wire 30, while leaving the guide wire 30 in place inthe treatment site. This is possible because the region 42 proximal tothe keyed portion 38 is sized to fit through the sleeve 64. Once theshaft 12 has been removed from the guide wire 30, a second catheter,which may or may not be similar to the catheter shown in FIG. 1, may beadvanced along the guide wire 30 directly to the original treatmentsite. Conventional extension wires may be used to facilitate theexchange. Alternately, the catheter may be designed such that the guidewire extends outside the catheter for the proximal portion of thecatheter and is received into the catheter for only the distal 15-30 cmof the catheter.

FIGS. 5 and 6 show portions of a second preferred embodiment of thecatheter assembly of this invention. This embodiment includes a catheter100 having a shaft that comprises a proximal tube 112 and a distal tube114 which are rigidly secured together at a point about 11 cm from thedistal end of the catheter 100 (at approximately the position of theplate 60 in the catheter 10). The proximal end of the proximal tube 112is secured to an inflation manifold (not shown) similar to the inflationmanifold 80. Similarly, the distal end of the distal tube 114 carries aballoon (not shown) similar to the balloon 30.

As shown in FIGS. 5 and 6, a spring carrier spyder 116 is fixed to thedistal tube 114, as for example by welding. The spyder defines four fins118 which support a tube 120 coaxially with the tube 114. The regionbetween the tubes 120, 114 forms four flow passages 122 that allow aninflation fluid to pass between the proximal and distal tubes 112, 114for inflation of the balloon (not shown).

Two coil springs 124, 126 are mounted within the tube 120, each fixed atone end by a respective spring tab 128, 130 which is securely fixed inplace on the tube 120. Both of the springs 124, 126 are formed ofrectangular section spring wire, and they are wound in the samedirection.

A guide wire 132 is positioned within the springs 124, 126, and theguide wire 132 may be configured at its proximal and distal ends (notshown) like the guide wire 30. The guide wire 132 defines an enlargedcylindrical portion 134 which in this embodiment is at least 10 andpreferably 15 cm in length. The enlarged cylindrical portion 134 issized to allow the catheter 100 to be removed from the proximal end ofthe guide wire 132 and to move longitudinally through the springs 124,126 freely in the absence of relative rotation between the catheter 100and the guide wire 132. However, when the catheter 100 is rotated ineither direction with respect to the guide wire 132, the respective oneof the springs 124, 126 automatically grips the guide wire 132 toprevent any relative rotation between the catheter 100 and the guidewire 132. Right hand rotation of the catheter 100 with respect to theguide wire 132 winds up the spring 124 and causes the spring 124 toseize the guide wire 132. Similarly, left hand rotation of the catheter100 with respect to the guide wire 132 winds up the spring 126 andcauses the spring 126 to seize the guide wire 132. In the absence ofrotation of the catheter in either direction, both of the springs 124,126 automatically relax, thereby automatically freeing the guide wirefor longitudinal movement in the catheter 100.

The catheter 100 and guide wire 132 can be used as described above suchthat the torsional rigidity of the catheter 100 applies torque to theguide wire 132 near the distal end of the guide wire 132.

Simply by way of example, in this preferred embodiment the proximal tube112 is formed of polyethylene, and the distal tube 114 is a stainlesssteel hypotube. Preferably, the spring carrier spyder is also formed ofstainless steel.

Of course, it should be understood that a wide range of changes andmodifications can be made to the preferred embodiment described above.As explained above, atherectomy devices or lasers may be used instead ofthe balloon 20 as a lumen size increasing means. Additionally, thetorque transmitting means does not necessarily include opposed flats asdescribed above. Rather, a wide range of geometries can be used as longas they achieve the dual purposes of allowing relative axial movementand transmitting torque. Additionally, the distal end of the guide wire30 can be altered in configuration and components as desired. Of course,materials and dimensions can be modified as desired to suit the intendedapplication.

It is therefore intended that the foregoing detailed description beregarded as illustrative rather than limiting, and that it be understoodthat it is the following claims, including all equivalents, which areintended to define the scope of this invention.

What is claimed is:
 1. A low profile catheter for increasing lumen sizeof a blood vessel, comprising:a catheter shaft having proximal anddistal ends and defining an axis extending therebetween; first means,carried by the distal end of the shaft, for increasing lumen size of ablood vessel in which the catheter shaft is positioned; a guide wirepositioned in the catheter shaft, said guide wire having proximal anddistal ends, said distal en extending beyond the distal end of thecatheter shaft and the lumen size increasing means; and second means forautomatically transmitting torque from the catheter shaft to the guidewire when the catheter shaft is rotated with respect to the guide wireand for automatically permitting relative axial movement therebetweenwhen the guide wire is advanced with respect to the catheter shaft saidsecond means located in said catheter shaft at least in part adjacent tosaid guide wire.
 2. The invention of claim 1 wherein the second means iscarried by the catheter shaft near the distal end of the catheter shaft,proximally of the lumen size increasing means.
 3. The invention of claim1 wherein the guide wire defines a keyed portion shaped to engage thesecond means.
 4. The invention of claim 1 wherein the second meanscomprises a keyed coupling member carried by the catheter shaft andshaped and positioned to receive the keyed portion of the guide wire. 5.The invention of claim 1 wherein the first means comprises an inflatableballoon.
 6. The invention of claim 1 wherein the guide wire has alength, and wherein the second means is configured to transmit torque tothe guide wire at a point spaced from the distal end of the guide wireby no more than 20% of the length.
 7. The invention of claim 6 whereinthe catheter shaft comprises a solid wall tube formed of a ferrous metalalloy.
 8. The invention of claim 6 wherein the guide wire has a maximumdiameter no greater than about 0.010 inches and a length no less thanabout 150 cm.
 9. The invention of claim 1 further comprising means,secured to the proximal end of the catheter shaft, for applying torqueto the catheter shaft.
 10. The invention of claim 3 wherein the keyedportion extends over a length of at least 10 cm to permit at least 10 cmof relative axial movement between the guide wire and the catheter shaftwhile retaining torque transmitting engagement between the cathetershaft and the guide wire.
 11. The invention of claim 1 wherein aproximal portion of the guide wire is sized and shaped to pass throughthe second means to permit the catheter shaft and the first means to beremoved from the proximal end of the guide wire.
 12. The invention ofclaim 1 wherein the second means comprises at least one coil springcarried by the catheter shaft and shaped and positioned to automaticallyseize the guide wire for rotation with the catheter shaft when thecatheter shaft is rotated in a first direction with respect to the guidewire by winding of the spring.
 13. The invention of claim 12 wherein theat least one coil spring comprises two coil springs, each shaped andpositioned to automatically seize the guide wire for rotation with thecatheter shaft when the catheter shaft is rotated in a respectivedirection with respect to the guide wire.
 14. A low profile dilationcatheter comprising:a catheter shaft having proximal and distal ends anddefining an axis extending therebetween; an inflatable balloon carriedby the distal end of the catheter shaft; a guide wire positioned in thecatheter shaft, said guide wire having proximal and distal ends, saiddistal end extending beyond the distal end of the catheter shaft andthrough the balloon, said guide wire defining a keyed portion having across sectional shape which is other than round; and a keyed couplingmember carried by the catheter shaft and coupled to the keyed portion ofthe guide wire, said keyed coupling member operative to transmit torquefrom the catheter shaft to the guide wire while permitting relativeaxial movement between the catheter shaft and the guide wire.
 15. Theinvention of claim 14 wherein the coupling member is positioned at thedistal end of the catheter shaft, proximal to the balloon.
 16. Theinvention of claim 14 wherein the keyed portion extends over a length ofat least 10 cm to permit at least 10 cm of relative axial movementbetween the guide wire and the catheter shaft while retaining torquetransmitting engagement between the catheter shaft and the guide wire.17. The invention of claim 14 wherein the guide wire proximal to thekeyed portion is sized and shaped to pass through the coupling member topermit the catheter shaft and balloon to be removed from the proximalend of the guide wire.
 18. The invention of claim 14 wherein thecoupling member comprises:a plate extending radially inwardly from thedistal end of the catheter shaft; and a sleeve positioned centrally ofsaid catheter shaft at the distal end of the catheter shaft by theplate, said sleeve defining an other than round opening sized to receivethe keyed portion of the guide wire to transmit torque to the guide wirewhile permitting relative axial movement between the sleeve and theguide wire.
 19. The invention of claim 18 wherein the plate ispositioned proximally of the balloon within the catheter shaft, andwherein the plate defines at least one opening positioned to pass aninflating fluid between the catheter shaft and the balloon.
 20. Theinvention of claim 14 further comprising means, secured to the proximalend of the catheter shaft, for applying torque to the catheter shaft.21. The invention of claim 14 wherein the guide wire defines an enlargedportion located distally of the keyed portion and sized to prevent theenlarged portion from passing through the coupling member.
 22. Theinvention of claim 18 further comprising a tube extending at least inpart through the balloon and secured to the distal end of the sleeve topass through the balloon, said tube receiving the guide wire andconducting the guide wire distally of the balloon.
 23. The invention ofclaim 14 wherein the catheter shaft is torsionally rigid.
 24. Theinvention of claim 14 wherein the catheter shaft comprises a solid walltube formed of a ferrous metal alloy.
 25. The invention of claim 14wherein the guide wire has a maximum diameter no greater than about0.010 inches and a length no less than about 150 cm.
 26. The inventionof claim 14 wherein the guide wire has a length, and wherein thecoupling member is positioned to transmit torque to the guide at a pointspaced from the distal end of the guide wire by no more than about 20%of the length.
 27. A low profile dilation catheter comprising:a cathetershaft having proximal and distal ends and defining an axis extendingtherebetween; a sleeve carried by the caterer shaft and having aninternal opening extending along the shaft and which is other thanround; means, carried by the distal end of the catheter shaft, forincreasing lumen size of a blood vessel in which the catheter shaft ispositioned; said sleeve operative to receive a guide wire axiallymovable in the sleeve and to transmit torque thereto; said lumen sizeincreasing means configured to pass the guide wire distally thereof. 28.The invention of claim 27 wherein the lumen size increasing meanscomprises an inflatable balloon.
 29. The invention of claim 27 whereinthe sleeve is positioned at the distal end of the catheter shaft. 30.The invention of claim 28 wherein the sleeve is positioned at the distalend of the catheter shaft, and wherein the sleeve is secured to thecatheter shaft by a support member which is provided with at least oneopening for passing an inflating fluid between the catheter shaft andthe balloon.
 31. The invention of claim 27 further comprising means,secured to the proximal end of the catheter shaft, for applying torqueto the catheter shaft.
 32. The invention of claim 28 further comprisinga tube secured to the distal end of the sleeve and passing through theballoon to conduct a guide wire distally thereof.
 33. The invention ofclaim 27 wherein the catheter shaft is torsionally rigid.
 34. Theinvention of claim 27 wherein the catheter shaft comprises a solid walltube formed of a ferrous metal alloy.
 35. A guide wire for a low profilecatheter for increasing lumen size of a blood vessel, said guide wirecomprising:a wire body having a proximal end and a distal end; aflexible end portion carried by the wire body at the distal end; saidwire body forming a region near the distal end, said region having across section which is other than round; said wire body having a maximumdiameter less than 0.020 inches.
 36. The invention of claim 35 whereinthe keyed region has a length greater than 10 cm.
 37. The invention ofclaim 35 wherein the maximum diameter is located distally region. 38.The invention of claim 35 wherein the wire body proximal to the regionis sized no larger than the region.
 39. The invention of claim 38wherein the wire body distal to the region is at least in part larger incross section than the region.
 40. The invention of claim 35 wherein theregion is substantially constant in cross sectional shape over adistance of at least about 10 cm.
 41. The invention of claim 35 whereinthe wire body has a maximum diameter no greater than about 0.010 inchesand a length no less than about 150 cm.
 42. The invention of claim 41wherein the region extends to a point separated from the end portion byno more than about 20% of the length of the wire body.
 43. A low profilecatheter for increasing lumen size of a blood vessel, comprising:acatheter shaft having proximal and distal ends and defining an axisextending therebetween; first means, carried by the distal end of theshaft, for increasing lumen size of a blood vessel in which the cathetershaft is positioned; a guide wire positioned in the catheter shaft, saidguide wire having proximal and distal ends, said distal end extendingbeyond the distal end of the catheter shaft and the lumen sizeincreasing means; and a first coil spring carried by the catheter shaftand positioned to surround the guide wire, said first coil springoperative to seize the guide wire for rotation with the catheter shaftwhen the catheter shaft is rotated in a first direction with respect tothe guide wire, and to release the guide wire for longitudinal movementwith respect to the catheter shaft when the catheter shaft is notrotated in the first direction with respect to the guide wire.
 44. Theinvention of claim 43 wherein the first coil spring is carried by thecatheter shaft near the distal end of the catheter shaft, proximally ofthe lumen size increasing means.
 45. The invention of claim 43 whereinthe first means comprises an inflatable balloon.
 46. The invention ofclaim 43 wherein the guide wire has a length, and wherein the coilspring is positioned in the catheter shaft to transmit torque to theguide wire at a point spaced from the distal end of the guide wire by nomore than 20% of the length.
 47. The invention of claim 43 wherein theguide wire defines a cylindrical portion sized to engage the first coilspring, wherein the cylindrical portion has a length of at least about10 cm.
 48. The invention of claim 43 wherein a proximal portion of theguide wire is sized and shaped to pass through the first coil spring topermit the catheter shaft and the first means to be removed from theproximal end of the guide wire.
 49. The invention of claim 43 furthercomprising a second coil spring carried by the catheter shaft andpositioned to surround the guide wire, said second coil spring operativeto seize the guide wire for rotation with the catheter shaft when thecatheter shaft is rotated in a second direction with respect to theguide wire, and to release the guide wire for longitudinal movement withrespect to the catheter shaft when the catheter shaft is not rotated inthe second direction with respect to the guide wire, wherein the firstand second directions are oppositely directed.
 50. A low profilecatheter for increasing lumen size of a blood vessel, comprising:acatheter shaft having proximal and distal ends and defining an axisextending therebetween; means, carried by the distal end of the shaft,for increasing lumen size of a blood vessel in which the catheter shaftis positioned; a first spring carried by the catheter shaft and wound ina selected direction, said first coil spring operative to receive aguide wire which is axially movable in the first coil spring in theabsence of rotation of the catheter shaft in a first direction, and toseize the guide wire for rotation with the catheter shaft when thecatheter shaft is rotated in the first direction with respect to theguide wire.
 51. The invention of claim 50 wherein the lumen sizeincreasing means comprises an inflatable balloon.
 52. The invention ofclaim 50 wherein the spring is positioned near the distal end of thecatheter shaft.
 53. The invention of claim 50 further comprising asecond coil spring carried by the catheter shaft and positioned tosurround the guide wire, said second coil spring operative to seize theguide wire for rotation with the catheter shaft when the catheter shaftis rotated in a second direction with respect to the guide wire, and torelease the guide wire for longitudinal movement with respect to thecatheter shaft when the catheter shaft is not rotated in the seconddirection with respect to the guide wire, wherein the first and seconddirections are oppositely directed.